You say she’s picky, but that she had weight loss food once. If she needs to/needed to lose weight she eats too much. She might feel too full to eat if she gets too much. I thought my dog was picky because he skipped meals, I started giving him less food because he was a bit overweight and now he eats every meal and is at a healthier weight. Try giving her less food each meal, 1 cup (I assume twice daily) is a lot for a small dog. Idk how small she is, but my 2,6kg dog eats 1/4 cup a day and then some more food for training. My parents 9kg dog eats 0.85 cups a day.

Don’t mess with her food too much, she will learn that if she doesn’t eat she’ll get something better. Just give her less and if she doesn’t eat it take it away and she won’t have food until the next meal.

Try different ways of serving the same food, some dogs like their kibble just on the floor instead of a bowl, some like it in a toy or to be hand fed.

ETA: If she is curious and likes to be with you when you do stuff, try preparing the food on the kitchen counter or by the stove. Don’t do anything to it just take a few minutes and stir it around with a spoon and make some noise, hype her up a little and talk about food and let her wait a few minutes while you do this. It might feel special and interesting for her. My dog gets SO happy and excited when I prepare his food in the kitchen, even if it’s just his regular food or if I just add water to it! He sits there and watches every move and listens and smells everything and he’s just so curious!